Speaking as a JOSM maintainer, I typically only want to add tags that match the following:
- Broad use (both in terms of users and in terms of total numbers) or general importance (there are only so many countries in the world, but we should still support them)
- I may make exceptions for tags that have been through the proposal process, if I think they might be generally useful. But someone has to open a ticket and provide a good icon.
- Our current threshold for “broad use” is 10k uses worldwide. We have a job that looks for these.
- Tag actually makes sense and is not going to be a typo of something else (specific example:
service=driveway and service=driveway2 – someone did think it would be a good idea)
- Non-controversial – I am not going to add tags that have had recent documentation changes or have otherwise been part of a controversy.
I typically put off adding new tags to JOSM since I have to create/find an icon for them.
See DevelopersGuide/DefaultPresets – JOSM for what we look for.
